The present invention generally relates to packaging and more particularly to an apparatus for making a package wrapped in a web of stretched film.
Case packing or boxing is a common way of shipping products. The products are generally stacked in a corrugated box or are wrapped with kraft paper with the end of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking the sleeve to form the unitized package.
Within the last five years, conventional packaging has significantly changed with the use of stretch film systems which wrap stretched film web around the load to hold the load in a tensioned unitized state. This efficient, commonly used packaging technique wraps the load with a single web of stretched plastic film web. This packaging is generally accomplished with apparatus commonly referred to as "full web wrapping" machinery, "spiral wrapping" machinery and "ring wrapping" machinery.
An early full web wrapping device which wraps stretched film around a rotating load carried by a turntable is described in U.S. Pat. No. 3,867,806. In this reference, an initial portion of the film wrap is placed on the load under a reduced tension and in a substantially unstretched state with the rest of the wrap being placed under an increased tension so that the film web is substantially stretched around the load to hold the package under compressive forces.
The use of spiral wrapping machinery is also well known in the art. A typical apparatus is shown by U.S. Pat. No. 3,863,425 in which film is guided from the roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load and deposits a spiral wrap around the load and returns in the opposite direction to deposit another spiral wrap around the load.
An early rotary type mechanism which rotates the film roll around a substantially stationary load to wrap the load with a stretched full web is shown in U.S. Pat. No. 4,079,565. In this reference, an arm carrying a film dispensing roll is rotatably mounted on a frame. The arm is rotatably driven by a motor so that the film roll carried on the distal end of the arm is transported around a stationary load supported by the tines of a fork truck, the load having previously been inserted into the wrapping area by positioning the load and fork truck tines within the wrapping area. In operation of the apparatus, the leading edge of the film web is pulled from the film roll by the operator and tucked into the fork truck load. The machine is activated by the operator and a plurality of full web wraps of stretched film are placed around the load and a pallet carrying the load to form a unitized package. The trailing end of the film web is then severed from the dispensing roll by the operator and sealed to the underlying film wrap. The package is carried out by the fork truck, removed from the tines of the truck and deposited in a storage area.
U.S. Pat. No. 4,050,220 discloses a wrapping device for multiple unit loads. Each load is conveyed to a wrapping area in which a load is supported on one or more stationary planar surfaces. The leading edge of a roll of stretchable plastic wrapping material is held adjacent to the load, and the roll of material is rotated on a ring mechanism about the load and the supporting planar surfaces, wrapping the load and the supporting surfaces together. The plastic wrapping material is stretched during the wrapping operation so that the material is placed under tension and stretched as applied to the load. After the wrapping cycle is complete, the wrapped load is pushed past the end of the supporting surfaces, and the wrapping material which originally covered the supporting surfaces collapses against the formerly supported side or sides of the load. Additional developments of ring driven wrapping systems are disclosed in U.S. Pat. Nos. 4,109,445; 4,110,957 and 4,178,734.
Another patent of interest, U.S. Pat. No. 4,226,397, a division of an application which issued into U.S. Pat. No. 4,166,348, is directed to a small package wrapping apparatus in which a driven rotatable disc is mounted on an upstanding frame. An independently driven package support mechanism is mounted on the rotatable disc along with another independently driven film dispenser mechanism. The film dispenser mechanism and support mechanism are rotated with planetary gearing keyed to the disc drive.
When the disc is rotated by the main drive assembly, the package support mechanism is rotated independently so that the upper surfaces of its supporting sections will at all times be maintained in a horizontal plane.
It can thus be seen that this apparatus, while adapted to hold and wrap small packages and loads, is constructed with very complex counter-rotating drive mechanisms causing relative rotation of the main disc, load support mechanism and dispenser mechanism.
Because of the nature of its complex construction, it is difficult to hold the film web during the start of the wrap requiring a mechanical tie to the load. Since the support mechanism moves, it is very difficult to support multiple units of irregular configuration such as a number of logs. Furthermore, the apparatus also suffers from not having a load hold down or clamping capacity.
Commercial circular rotating wrapping machines are presently manufactured by Lantech Inc. under the trademark LANRINGER and are provided with wrapping rings having inner diameters of thirty six inches, fifty four inches, seventy two inches and eighty four inches. The roll of stretch material is carried on these wrapping rings. In differentiating between these various circular rotating wrapping machines manufactured by Lantech Inc., the manual model has the designation "SR", the full web models have the designations "SVR" and "SAVR", the multiple banding models have the designation "SVBR" and "SAVBR", the spiral models have the designation "SVSR" and "SAVSR", and the continuous wrap or bundler models have the model designations "SVCR" and "SAVCR".
In these commercial machines, the load is pushed from a conveyor onto support tongues or wrapping rails and the load and support tongues are wrapped by a supply of stretch film carried by the wrapping ring. The film is stretched as it is rotated from the dispenser and the stretched film holds the load together under compressive forces and also engages the tongues or wrapping rails on which the load is supported. The load is then pushed or carried off of the tongues by the following load or a take off conveyor. Alternately, the load as it is fed into the rotating wrapping apparatus is carried through the wrapping station by a conveyor assembly having an upper conveyor which carries the load in a downstream direction and a lower conveyor mounted under the load carrying conveyor. The lower portion of the endless belt of the lower conveyor travels at the same speed and in the same direction as the upper portion of the endless belt of the load carrying conveyor so that stretched film wrapped around the load and conveyor assembly is carried by the lower conveyor at the same speed and in the same direction as the load is carried by the upper conveyor.
As previously noted, the popularity in the use of stretched plastic film for wrapping loads occurs because the elasticity of the stretched plastic film on the products of the load holds the load under more tension than either shrink wrap or kraft wrap, particularly with products which settle when packaged. The effectiveness of stretched plastic film in holding a load together is a function of the containment or stretch force being placed on the load, and the ultimate strength of the total layered film wrap. These two functions are determined by the modulus, or hadrness, of the film after stretch has occurred and the ultimate strength of the film after application.
Generally speaking, the aforementioned commercial wrapping machines are generally not susceptible for use by operators who are interested only in the manual wrapping of small loads, without the need of expensive automatic apparatus.
It can thus be seen that there is a need for a simply constructed, manually operated apparatus which is provided with a stable wrapping platform. The apparatus should be constructed to allow an operator to reach into the wrapping area without fear of injury, have relatively few maintenance and replacement problems, and be easily operated by relatively unskilled personnel.